Compact transformer with integral connector

ABSTRACT

A compact transformer which may be used with a recharging circuit for portable electronic devices is illustrated having integral connector blades for mating with an AC power outlet, such as a wall socket. The transformer windings are wound on a standard coil bobbin having a central aperture. The connector blades pass through the central aperture and are clamped therein by the laminated core material of the transformer. An insulative laminate is used to divide the core into two sections in order to electrically isolate the two connector blades from each other. The resulting transformer may have rectifying components attached thereto and may be encapsulated for environmental protection.

United States Patent Holden et al.

[451 Oct. 21, 1975 COMPACT TRANSFORMER WITH INTEGRAL CONNECTOR App]. No.: 485,395

3,237,079 2/1966 Mas 336/107 X 3,354,417 11/1967 Davis 336/198 FOREIGN PATENTS OR APPLICATIONS 1,213,910 4/1966 Germany 336/192 Primary ExaminerThomas J. Kozma Attorney, Agent, or Firm-Patrick J. Barrett [57] ABSTRACT A compact transformer which may be used with a recharging circuit for portable electronic devices is illustrated having integral connector blades for mating with an AC power outlet, such as a wall socket. The transformer windings are wound on a standard coil bobbin having a central aperture. The connector blades pass through the central aperture and are clamped therein by the laminated core material of the transformer. An insulative laminate is used to divide the core into two sections in order to electrically isolate the two connector blades from each other. The resulting transformer may have rectifying components attached thereto and may be encapsulated for environmental protection.

7 Claims, 7 Drawing Figures Sheet 1 of 2 3,914,658

US. Patent Oct. 21, 1975 U.S. Patent Oct. 21, 1975 Sheet 2 of2 3,914,658

COMPACT TRANSFORMER WITH INTEGRAL CONNECTOR BACKGROUND OF THE INVENTION FIG. 1 shows a transformer coil bobbin. FIG. 2 shows an exploded view of a preferred em Many portable electronic devices available today opbodiment of the present invention.

ate on rechargeable batteries and must therefore be :riodically connected to a source of power for reiarging the batteries. Since one of the objects in derloping portable electronic devices is to reduce the :e and weight of these devices it is desirable to have recharging circuit separate from the device but which ay be easily connected to the device. To fulfill this irpose, a number of compact recharging devices are lrrently available in which a transformer and some ctifying components are included in a case that has connector for mating with common AC power outts. These devices typically have a number of separate )mponents such as the transformer, a printed circuit Jard for mounting various components and the con- :ctor itself and all these items must be connected to- :ther to form a completed assembly.

In order to reduce cost and improve the compactness these devices, transformers have been developed ith special coil bobbins that hold not only the transrrmer windings but also the connector blades for con- :cting with the AC power outlet. Two such prior art :vices are illustrated by US. Pat. Nos. 3,371,302 and 237,079. The first patent shows a bobbin having the iual central aperture for the transformer core and two iditional apertures alongside the central aperture for Jlding the connector blades. Wires from the trans- Irmer primary are in turn connected to these transrrmer blades. The second-mentioned patent shows anther special form of bobbin having slots in the bobbin de wall to permit the blades to be inserted in the windrgs themselves while the transformer is being wound that the blades are held in place by wire. Both of iese prior art devices have the significant disadvanige that a special purpose bobbin is required; and, aliough the need for additional mounting components r the connector blades is reduced, costs are increased ue to the cost of manufacturing special bobbins.

SUMMARY OF THE INVENTION It is an object of this invention to provide a compact ansformer having connector members integral thereith without requiring the use of a special purpose ansformer bobbin.

In accordance with the illustrated embodiment of the resent invention the transformer coils are wound on standard bobbin having a single central aperture runing through the tubular portion of the bobbin. A stanard laminated core is then placed around the translrmer windings and through the central aperture of [C bobbin and the connector blades are also inserted trough the central aperture of the bobbin and are amped therein by the core. Clamping the connector lades in the central aperture of the bobbin with the )re material results in a live" core, that is, a core that at the same voltage as the primary winding. In order a prevent shorting of the voltage across the primary inding, an insulative member is inserted between two t'the transformer core laminates to make two electriilly isolated portions. Various rectifying components in be mounted on the insulative member and the enre assembly can be encased or encapsulated for proction from-the environment.

FIGS. 3 and 4 show other preferred embodiments of connector blades.

FIG. 5 shows an assembled transformer.

FIG. 6 shows an insulative laminate with electrical components mounted thereon.

FIG. 7 shows an encapsulated transformer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a bobbin 10 having a tubular portion 12 with an aperture therethrough 14 and side walls 16 and 18. Bobbins of the type illustrated are commercially available in a number of sizes and form factors and are usually made of an insulative material such as plastic. The primary and secondary windings of the transformer are wound on this bobbin according to wellknown methods and the windings may be secured or covered by various insulating materials such as mylar electrical tape.

After the primary and secondary windings have been wound on the bobbin, the transformer core 20 is assembled. As shown in FIG. 2, bobbin 10 with windings 22 has a plurality of E-shaped ferrous laminates inserted through the aperture in the bobbin and around two sides of the windings. The core is completed by shaped ferrous laminates 26 which are placed across the open ends of the E-shaped laminates 24. A sufficient number of laminates is added so that the aperture 14 is almost filled with the core material. The remaining space is occupied by an electrically insulating laminate or layer 28 and a pair of contact blades 30 and 32.

The connector blades 30 and 32 are made of a resilient, conductive material such as brass; and ends 34 and 36 respectively of these blades are fashioned to connect with a common AC power outlet. The blades are retained in aperture 14 by friction between the blades and the surfaces of the bobbin and the core material that they contact. Additionally, a retainer pin 38 can be passed through holes 40a through e in the connector blades, the insulating layer and the lshaped laminates. The E- and l-shaped laminates comprising the transformer core are retained by electrical tape 42 wrapped around the core or by other well-known means of retaining transformer core pieces such as keepers and shellacking.

FIGS. 3 and 4 show alternate forms of the connector blades. In FIG. 3 connector blade 30' is the same as the connector blades in FIG. 2 except for a tab 31 with a hole 33. Transformer primary leads 44 may be inserted into the hole in the tab on each connector blade for attachment by soldering or crimping. Alternatively, primary leads 44 may be soldered to one of the exposed surfaces on connector blades 30 and 32. The connector blade may also be straight, as shown in FIG. 4, rather than the dog-leg shape of the connector blades shown in FIGS. 2 and 3. The ability to connect the primary leads directly to the connector blades eliminates the need for connection between the AC connector and the transformer via separate leads, terminals, printed circuit board paths or the like. As shown in FIG. 2, secondary leads 46 from the transformer may be connected directly to a cable that carries the transformed voltage to another device such as a portable electronic instrument.

Although it is often convenient to place rectifying filtering or current limiting components in the utilization device, some or all of those components can also be mounted on the transformer. As shown in FIG. 6, rectifying components such as a diode 60, current limiting components such as a resistor 62 and filtering components such as a capacitor 64 may be mounted on insulating layer 28'. In order to connect these components together the insulating layer 28 may comprise a printed circuit board having conductive paths or traces. It will be noted that insulating layer 28' has been made larger than insulating layer 28 illustrated in FIG. 2 so that the portions on which the components are mounted protrude beyond the core. The location of the periphery of the core is illustrated by the dotted line in FIG. 6. To facilitate connection of secondary leads 46 to components on insulating layer 28' terminals such as printed circuit pads 68 may be provided on the insulating layer.

FIG. 7 illustrates a housing 50 around the transformer and any components which may be connected thereto. The housing may be formed, for example, by encapsulation in a plastic material, or it may be an assembled case.

Although applicants have found that there are no apparent adverse effects from having a live core, that is, a transformer core that is at the same potential as the primary windings, alternate methods of electrical isolation between the connector blades may be provided. For example, the portion of the blade that is in contact with the transformer core may be coated with an insulative material such as a plastic encapsulant, as may the core material. Alternatively insulative layer 28 may be placed immediately adjacent one of the connector blades so that it is insulated from the core; or both blades may be insulated from the core in this manner, if it is desired to have a core insulated from the supply potential.

We claim:

1. A transformer comprising:

a bobbin having an aperture therethrough;

a primary transformer winding and a secondary transformer winding wound on the bobbin;

a transformer core having a cental core portion passing through and substantially filling the aperture in the bobbin;

a first one-piece, blade-shaped connector member for making connection with an electrical power outlet and clamped between and in direct contact with the inner surface of the bobbin aperture and the central core portion to restrain movement of the first connector member in the bobbin aperture;

and

a second one-piece, blade-shaped connector member for making connection with an electrical power outlet, clamped between the inner surface of the bobbin aperture and the central core portion to re strain movement of the second connector member in the bobbin aperture, and electrically insulated from the first connector member.

2. A transformer as in claim 1 further comprising insulation means dividing the central core portion into two electrically isolated portions.

3. A transformer as in claim 2 wherein the trans former core comprises a plurality of ferrous laminates the insulation means comprises a layer of insulative material between two of the ferrous laminates.

4. A transformer as in claim 3 including electrical components connected to the secondary transformer winding and mounted the layer of insulative material.

5. A transformer as in claim 2 wherein the transformer is encapsulated in an insulative material.

6. A transformer as in claim 1 wherein the first and second connector members each have three portions, a first portion for making connection with an electrical power outlet, a second portion parallel to the first portion and clamped between the bobbin aperture and a surface of the core portion, and a third portion essentially orthogonal to and connecting the first and second portions.

7. A transformer as in claim 1 further comprising insulation means between the second connector member and the central core portion.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3, 914,658

DATED I October 21, 1975 VENTOMS) 1 Thomas E. Holden and Mark S. Linsky It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 29, after "mounted" insert on Signed and Scaled this s th D3 of 11 y January 1976 Arrest:

RUTH C. M KSON C. MARSHALL DANN Alrfllmg 011m (ummissrmrvr nj'Palenrs and Trademarks 

1. A transformer comprising: a bobbin having an aperture therethrough; a primary transformer winding and a secondary transformer winding wound on the bobbin; a transformer core having a cental core portion passing through and substantially filling the aperture in the bobbin; a first one-piece, blade-shaped connector member for making connection with an electrical power outlet and clamped between and in direct contact with the inner surface of the bobbin aperture and the central core portion to restrain movement of the first connector member in the bobbin aperture; and a second one-piece, blade-shaped connector member for making connection with an electrical power outlet, clamped between the inner surface of the bobbin aperture and the central core portion to restrain movement of the second connector member in the bobbin aperture, and electrically insulated from the first connector member.
 2. A transformer as in claim 1 further comprising insulation means dividing the central core portion into two electrically isolated portions.
 3. A transformer as in claim 2 wherein the transformer core comprises a plurality of ferrous laminates the insulation means comprises a layer of insulative material between two of the ferrous laminates.
 4. A transformer as in claim 3 including electrical components connected to the secondary transformer winding and mounted the layer of insulative material.
 5. A transformer as in claim 2 wherein the transformer is encapsulated in an insulative material.
 6. A transformer as in claim 1 wherein the first and second connector members each have three portions, a first portion for making connection with an electrical power outlet, a second portion parallel to the first portion and clamped between the bobbin aperture and a surface of the core portion, and a third portion essentially orthogonal to and connecting the first and second portions.
 7. A transformer as in claim 1 furtHer comprising insulation means between the second connector member and the central core portion. 